Polarization-universal radial line slot antenna

ABSTRACT

A polarization-universal radial line slot antenna has a slot plate formed with numerous slots, a frame, and a partition plate interposed between the slot plate and the frame to form an upper layer waveguide and a lower layer waveguide. A pair of first and second feeding devices are provided in a central portion of the antenna. The first feeding device has a first matching member protruding into the upper layer waveguide for feeding thereto a radio wave diverging from a center to a periphery so that a left-hand circular polarized wave is emitted from the slots. The second feeding device has a second matching member for feeding a radio wave which passes through the lower layer waveguide and then converges from a periphery to a center of the upper layer waveguide so that a right-hand circular polarized wave is emitted from the slots. Consequently, the single antenna can concurrently transmit or receive the right-hand and left-hand circular polarized waves.

FIELD OF TECHNOLOGY

The present invention relates to a radial line slot antenna utilizing aradial waveguide for use in SHF and EHF bands.

BACKGROUND FIELD

Conventionally, a parabolic antenna having a bowl shape is used in asatellite communication or else; however, recently a radial line slotantenna is developed instead of the parabolic antenna.

The radial line slot antenna is disclosed, for example, in JapanesePatent Publication No. 1-13241. Namely, a pair of metal disks areopposed to each other through a spacing, one of which is formed withslots for power emission. A peripheral metal wall is fitted along edgesof these metal disks to form an inner waveguide spacing enclosed bythese metal disks and the peripheral wall. A feeding means is providedto feed a power to the waveguide spacing such that the fed power isconverged to a central portion of the waveguide spacing from theperipheral wall. The feeding means is comprised of a feeding sourceconnected to the waveguide spacing, and an intermediate metal platedisposed in parallel to the pair of the metal disks such as to leave agap relative to the peripheral wall within the waveguide spacing toprovide a return pass of the fed power.

Generally, with regard to a circular polarized electromagnetic radiationhaving a certain frequency, there exist a right-hand circularpolarization which rotates rightward in a traveling direction, and aleft-hand circular polarization which rotates leftward in a travelingdirection. However, the conventional radial line slot antenna cannot beused commonly to both of the right-hand and left-hand circularpolarizations. Therefore, there is a drawback that a separate pair ofantenna must be installed for the right-hand and left-hand circularpolarization waves, though these waves have the same frequency.

In view of the above noted drawback, an object of the present inventionis to provide a polarization-universal radial line slot antenna whichcan be commonly used for either of the right-hand and left-hand circularpolarizations.

DISCLOSURE OF THE INVENTION

According to the invention, the radial line slot antenna comprises aslot plate having numerous slots, a frame opposed to the slot plate, apartition plate interposed between the slot plate and the frame to forman upper layer waveguide and a lower layer waveguide, and feeding meansfor feeding these waveguides. Characterizingly, the feeding meanscomprises first feeding means composed of a coaxial line having a tipend portion which protrudes through the partition wall into the upperlayer waveguide to feed the same, and second feeding means composed of adielectric member and a conductor member, which are formed coaxiallyaround the coaxial line to feed the lower layer waveguide.

Further, according to the present invention, the polarization-universalradial line slot antenna comprises a slot plate having numerous slots, aframe opposed to the slot plate, a partition plate interposed betweenthe slot plate and the frame to form an upper layer waveguide and alower layer waveguide, and feeding means for feeding these waveguides.Characterizingly, the feeding means comprises a coaxial line disposedmovably through an opening formed in a central portion of the partitionplate, and a conductor piece attached to a tip end portion of thecoaxial line and having a diameter greater than that of the opening.

In the inventive polarization-universal radial line slot antenna, aradio wave is fed to the upper layer waveguide by means of the firstfeeding means, and the same radio wave is also fed to the lower layerwaveguide by means of the second feeding means. In such a construction,the slots are aligned along a spiral pattern which, for example, expandsclockwise from the center, hence the slots are excited sequentially fromthe central ones to the peripheral ones when the upper layer waveguideis fed by the first feeding means, so that a left-hand circularpolarized wave is emitted from the antenna. Further, when the lowerlayer waveguide is fed by the second feeding means, consequently theslots are sequentially excited from peripheral ones to the central onesso that a right-hand circular polarized wave is emitted, which rotatesreversely to the aforementioned left-hand circular polarized wave,thereby achieving the object of the polarization-universal antenna.Further, the first and second feeding means are operated independentlyfrom each other so that both of the right-hand and left-hand circularpolarized waves can be emitted concurrently with each other.

Further, in the other polarization-universal radial line slot antenna ofthe invention, the coaxial line is displaced integrally with absorptionmembers such that the absorption members pass through respective holesformed in the central portions of the slot plate and the frame, whilethe coaxial line passes through the opening formed in the centralportion of the partition plate, thereby selectively feeding either ofthe upper layer waveguide and the lower lager waveguide. In case thatthe slots are arranged along a spiral pattern which expands clockwisefrom the center to the periphery, when the upper layer waveguide is fedwith a power, the slots are successively excited from central ones tothe peripheral ones to thereby emit a radio wave of the left-handcircular polarization. On the other hand, when the lower layer waveguideis fed with a power, consequently the slots are excited successivelyfrom the peripheral ones to the central ones to thereby radiate a radiowave of the right-hand circular polarization which rotates reversely tothe aforementioned case. Therefore, the antenna can be selectively andcommonly used for either of the left-hand and right-hand circularpolarizations to thereby achieve the object of thepolarization-universal antenna construction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an axially sectional diagram showing an overall constructionof one embodiment according to the invention, FIG. 2 is a partialperspective view thereof, FIG. 3 perspective diagram illustrative offeeding of an upper layer waveguide in another embodiment of theinvention, FIG. 4 is an axially sectional diagram illustrating feedingof a lower layer waveguide in said another embodiment, and FIG. 5 is aplan view of a slot arrangement.

BEST MODE FOR PRACTICING THE INVENTION

Referring to FIGS. 1 and 2, the antenna is provided with a slot plate 1composed of a metal disk having numerous slots 2 formed by etchingprocess or else. The slots 2 are arranged along a clockwise orcounterclockwise spiral pattern which expands outward at a pitch of awaveguide wavelength λg when rotated. For example, as shown in FIG. 5,numerous slots having a T-shape are aligned along a clockwise spiralpattern.

A frame 3 is formed by drawing a peripheral portion of a metal diskmaterial. This peripheral portion is coupled to the slot plate 2, and issealed by an epoxy resin or else. Further, a partition plate 5 isinterposed between the slot plate 1 and the frame 3 to internally forman upper layer radial waveguide 4, a lower layer radial waveguide 6, anda folded return pass 40 at a periphery.

A redome 8 is fitted on the slot plate 1 to prevent penetration of rainwater or else. The radome 8 is molded by Teflon material or other smoothmaterials effective to avoid snow cover or else, and a periphery thereofis engaged with the frame 3 by sealing. If necessary, a spacer (notshown) composed of styrene foam or else may be inserted into a spacing 7between the radome 8 and the slot plate 1. Further, a high foamingdielectric member may be filled into the lower layer radial waveguide 6.

First feeding means is provided in a central portion of the partitionplate 5, and is composed of a coaxial line comprised of a core conductormember 9, a first dielectric member 32 and a first outer conductormember 31. Further, second feeding means is composed of a seconddielectric member 22 disposed around the first outer conductor member31, and a second outer conductor member 3' integrated with the frame anddisposed coaxially with the first outer conductor member 31.

A transducer 20 is provided under the first and second feeding means,and has a waveguide tube 24 for feeding the lower layer radial waveguide6 and another waveguide tube 25 for feeding the upper layer radialwaveguide 4.

A second matching member 21 is provided around the first outer conductormember 31 within the lower layer radial waveguide 6.

Tip end portions of the core conductor member 9 and the first dielectricmember 32 protrude upward through the partition plate 5. A firstmatching member 33 is disposed on top of the core conductor member 9. Abottom end of the core conductor member 9 protrudes together with thefirst dielectric member 32 into the waveguide tube 25 which is disposedunder the other waveguide tube 24. On the other hand, the seconddielectric member 22 has an axial length extending between the bottom ofthe lower layer radial waveguide 6 and the top of the waveguide tube 24.The second outer conductor member 3' is formed integrally with the frame3 and the transducer 20.

Next, description is given to the feeding operation of the radial lineslot antenna having the above disclosed construction. In the radial lineslot antenna of the present embodiment, the waveguide tube 25 of thetransducer 20 feeds an electromagnetic wave, which passes through thefirst feeding means, i.e., the coaxial line composed of the coreconductor member 9, the first dielectric member 32 and the first outerconductor member 31, and which is then introduced into the upper layerradial waveguide 4 through the first matching member 33. Consequently,an axially symmetric radio wave of a most basic mode diverging from thecenter to the periphery is emitted from slots 27, 28 as a left-handcircular polarized wave, in case that the slots are arranged along aspiral pattern 26 which expands clockwise from the center as shown inFIG. 2.

Further, the first outer conductor member 31 functions as a coreconductor member of the second feeding means. Namely, the waveguide tube24 feeds an electromagnetic wave, which passes through another coaxialline composed of the first outer conductor member 31, the seconddielectric member 22 and the second outer conductor member 3', and whichis then introduced into the lower layer radial waveguide tube 6 by meansof the second matching member 21. Consequently, an axially symmetricwave diverges from the center to the periphery within the lower layerradial waveguide 6, and is then folded into the upper layer radialwaveguide 4 through the peripheral return pass 40 to thereby form aradio wave which converges to the center from the periphery, and whichis finally emitted from slots 29, 30 as a right-hand circular polarizedwave as shown in FIG. 2.

By such a construction, both of the right-hand and left-handpolarizations can be concurrently treated by the pair of the first andsecond feeding means. This is due to a two-wave coexistence performancewhich is basic in the radial waveguide. In the present embodiment, a lowfoaming dielectric material may be filled in the upper layer radialwaveguide 4 for wave delay, and a high foaming dielectric material maybe filled in the lower layer radial waveguide 6.

Next, another embodiment of the present invention will be described inconjunction with FIGS. 3 and 4. In these figures, the antenna isprovided with a slot plate 1 composed of a metal disk having numerousslots formed by etching process. The slots 2 is arranged along arightward or leftward spiral pattern which expands outward at a pitch ofa waveguide wavelength λg when the slot plate is rotated. For example,as shown in FIG. 5, numerous slots of T-shape are aligned along aclockwise spiral pattern.

A frame 3 is formed by drawing a periphery of a metal disk material. Theslot plate 1 is coupled to this periphery and is sealed by an epoxyresin or else along the periphery. Further, a partition plate 5 having acentral opening 18 is interposed between the slot plate 1 and the frame3 to form internally an upper layer radial waveguide 4, a lower layerradial waveguide 6, and a peripheral folded return pass 41. Further, anabsorption member 10, a core conductor member 9 and a dielectric member11 are fitted into a central portion of the slot plate 1. Moreover, anouter conductor member 19 and another absorption member 12 are disposedcoaxially around the dielectric member 11.

These core conductor member 9, the dielectric member 11 and the outerconductor member 19 constitute a coaxial line, a lower end portion ofwhich is connected to a transducer 20 of a two-layer structure. Thistransducer 20 has an internal separating wall 15 to divisionally form atop layer waveguide tube 14 for feeding the upper layer radial waveguide4 and a bottom layer waveguide tube 16 for feeding the lower layerradial waveguide 6.

A redome 8 is fitted over the slot plate 1 to prevent penetration ofrain water or else. This redome 8 is molded with a Teflon or othersmooth materials effective to avoid snow deposit or else. A peripherythereof is engaged with the frame 3 and is sealed thereto. If necessary,a spacer (not shown) such as a styrene foam may be filled in a spacing 7between the radome 8 and the slot plate 1. In manner similar to theprevious embodiment, a high foaming dielectric member may be filledwithin the lower layer radial waveguide 6.

Next, specific description is given to those of the core conductormember 9, dielectric member 11, and pair of absorption members 10, 12.The absorption member 10 is smaller than a hole 17 formed in a centralportion of the slot plate 1 so that the absorption member 10 candisplace up and down through the hole 17 relative to the slot plate 1.

The core conductor member 9 has a T-shape section such that a top piece9a thereof has a size greater than the opening 18 of the partition plate5 so as to close the opening 18. The absorption member 10 is disposed onthe top piece 9a of the core conductor member 9.

The coaxial line composed of the core conductor member 9 coveredcoaxially by the dielectric member 11 and the outer conductor 19 extendsdownward from the center of the partition plate 5 through another hole3a formed in a central bottom portion of the frame 3. The outerconductor member 19 of the coaxial line has a flange at the top endportion thereof so as to close the hole 3a. The flange is positioned inspaced relation from the top piece 9a of the core conductor member 9 toprovide an upper exposed portion 11a along the dielectric member 11between the top piece 9a and the flange. Further, the outer conductormember 19 is shaped to provide a lower exposed portion 11b along thedielectric member 11.

The other absorption member 12 is disposed around the outer conductormember 19 to pass through the hole 3a. The absorption member 10, coreconductor member 9, dielectric member 11, outer conductor member 19 andabsorption member 12 constitute altogether the feeding means which candisplace up and down.

The description is given to switching operation of the feeding means.The feeding means is displaced upward in order to feed the upper layerradial waveguide 4. Namely, as shown in FIG. 3, the absorption member 10is positioned between the slot plate 1 and the radome 8, while the toppiece 9a of the core conductor member 9 closes the hole 17 of the slotplate 1. Further, the upper exposed portion 11a of the dielectric member11 is placed in the upper layer radial waveguide 4, the flange of theouter conductor member 19 contacts the partition plate 5, the absorptionmember 12 is placed in the lower layer radial waveguide 6, and the lowerexposed portion 11b of the dielectric member 11 is positioned in theupper waveguide tube 14 of the transducer 20.

Accordingly, in case that the feeding means is set in the position ofFIG. 3, the upper waveguide tube 14 feeds an electromagnetic wave to thedielectric member 11 through the lower exposed portion 11b. Theelectromagnetic wave is then fed to the upper layer radial waveguide 4from the upper exposed portion 11a. Consequently, a most basic radiowave of an axially symmetric mode diverging from the center to theperiphery is emitted from slots 27, 28 in the form of a left-handcircular polarized wave, in case that the slots are arranged along thespiral pattern 26 which expands rightward from the center. Further, theremaining radio wave which has not been emitted is absorbed by theabsorption member 12 in the lower layer radial waveguide 6.

Next, the feeding means is displaced downward in order to feed the lowerlayer radial waveguide 6. As shown in FIG. 4, the absorption member 10is positioned between the slot plate 1 and the partition plate 5, andthe top piece 9a of the core conductor member 9 closes the opening 18 ofthe partition plate 5. Further, the upper exposed portion 11a of thedielectric member 11 is positioned in the lower layer radial waveguide6, the flange of the outer conductor member 19 comes into contact with aperiphery of the hole 3a in the bottom central portion of the frame, theother absorption member 12 is positioned outside the frame, and thelower exposed portion 11b of the dielectric member 11 is placed in thelower waveguide tube 16 of the transducer 20.

Accordingly, when the feeding means is set in the position of FIG. 4,the lower waveguide tube 16 feeds a radio wave to the dielectric member11 through the lower exposed portion 11b. The radio wave is then fed tothe lower layer radial waveguide 6 from the upper exposed portion 11a ofthe dielectric member 11. Consequently, an internal radio wave divergesradially from the center to the periphery in the lower layer radialwaveguide 6, and is then folded by the peripheral return pass 41 tothereby travel into the upper layer radial waveguide 4 to converge fromthe periphery to the center. Consequently, a right-hand circularpolarization wave is emitted from slots 29, 30.

In the radial line slot antenna of this embodiment, the feeding means isswitched as described above to select either of the right-hand andleft-hand circular polarized waves.

Industrial Applicability

As described above, the inventive radial line slot antenna can commonlydeal with either of the right-hand and left-hand circular polarizations.Thus, a single antenna can be used to transmit and receive anelectromagnetic wave of a satellite broadcast or else.

We claim:
 1. A polarization-universal radial line slot antennacomprising: a slot plate having numerous slots; a frame opposed to theslot plate; a partition plate interposed between the slot plate and theframe to form an upper layer waveguide and a lower layer waveguide; andfeeding means for feeding these waveguides, wherein the feeding meanscomprises first feeding means composed of a coaxial line having a tipend portion which protrudes through the partition plate into the upperlayer waveguide so as to feed the same, and second feeding meanscomposed of a dielectric member and a conductor member which arecoaxially disposed around the coaxial line so as to feed the lower layerwaveguide.
 2. An antenna apparatus comprising an upper slot plate havingnumerous slots; a lower frame opposed to the upper slot plate; anintermediate partition plate interposed between the upper slot plate andthe lower frame so as to form an upper radial waveguide between theupper slot plate and the intermediate partition plate, a lower radialwaveguide between the intermediate partition plate and the lower frame,and a peripheral pass connecting between the upper radial waveguide andthe lower radial waveguide; and feeding means provided axially through acentral portion of the partition plate for feeding a radio wave to theupper radio waveguide so that the radio wave radially diverges throughthe upper radio waveguide to successively excite the slots in a radiallyoutward direction, and for feeding another radio wave to the lowerradial waveguide so that the radio wave diverges through the lowerradial waveguide in a radially outward direction and then enters intothe upper radial waveguide through the peripheral pass to convergethrough the upper radial waveguide to thereby successively excite theslots in a radially inward direction.
 3. An antenna apparatus accordingto claim 2; wherein the feeding means comprises first feeding meansfixedly disposed in the upper radial waveguide for feeding thereto aradio wave, and second feeding means fixedly disposed in the lowerradial waveguide for feeding thereto another radio wave.
 4. An antennaapparatus according to claim 3; wherein the first feeding meanscomprises a coaxial line having a tip end portion protruding through thecentral portion of the partition plate into the upper radial waveguide,and the second feeding means comprises a dielectric member and an outerconductor member, which are disposed coaxially around the coaxial line.5. An antenna apparatus according to claim 4; wherein the first feedingmeans has a first matching member disposed on the tip end portion of thecoaxial line, and the second feeding means has a second matching memberformed around the central portion of the partition plate.
 6. An antennaapparatus according to claim 2; wherein the feeding means comprisesmovable feeding means displacable axially in the central portion of thepartition plate, and being switchable between an upper position forselectively feeding a radio wave to the upper radial waveguide and alower position for selectively feeding another radio wave to the lowerradial waveguide.
 7. An antenna apparatus according to claim 6; whereinthe movable feeding means comprises a coaxial line having a tip andportion which is placed in the upper radial waveguide when the movablefeeding means is switched to the upper position, and which is placed inthe lower radial waveguide when the movable feeding means is switched tothe lower position.
 8. An antenna apparatus according to claim 7;wherein the movable feeding means has an upper absorption memberdisposed on the tip end portion of the coaxial line for absorbing aremaining radio wave and being placed in the upper radial waveguide whenthe movable feeding means is switched to the lower position, and a lowerabsorption member fitted around the coaxial line for absorbing aremaining radio wave and being placed in the lower radial waveguide whenthe movable feeding means is switched to the upper position.
 9. Anantenna apparatus according to claim 2; wherein the slot plate hasnumerous slots arranged along a spiral pattern such that the slots canemit one of right-hand and left-hand circular polarized waves when theradio wave diverges through the upper radial waveguide, and can emit theother of right-hand and left-hand circular polarized waves when theradio wave converges through the upper radial waveguide.